wrote
PEX? I like it, but have never worked with it, and I don't have the right
tools.

Check out these guys. Look into using compression fittings instead of
special tools.
http://www.pexsupply.com/resources/pexPlumbing


PVC? Indoors?

My gut choice for this is polyethylene tubing, the same stuff we use to
pipe
the refrigerator's ice maker. Very affordable and easy to snake through
enclosed spaces with no joins. I used the 3/8" stuff a few years ago to
add
a filter housing to my kitchen sink, using the push-lock poly fittings.
Very easy and no leaks to date. But is it anything like code compliant?

In a harsh environment, it can be brittle and burst. I'd not use it in a
hidden area like a garage attic.